The present invention relates to an active optical image enhancer for a microscope.
Currently, microscopy systems, including fluorescence microscopy systems, suffer from poor performance due to inherent limitations in the microscope instrumentation itself. The major drawback associated with conventional microscopy is the out-of- focus stray light that causes the image to be severely degraded. Confocal microscopes overcome the stray light problems by including complex mechanical equipment that filters out the unwanted stray light. All confocal microscopes use a tiny pinhole or slit to force the microscope to only focus on one layer. Thus, the out-of-focus stray light is virtually eliminated making it possible to study thicker specimens and to make 3D reconstructions of the specimens. However, the tiny pinhole (often 20 microns in diameter) severely restricts the amount of light throughput making it difficult to detect low light FISH signals.
The inventive system enables an image with a large depth of field to be formed. One particular application is FISH (Fluorescent in-situ hybridization). The ability to spatially locate segments of DNA, RNA and proteins in tissues and individual cells is rapidly providing new information in many fields including all areas of cancer research, diagnosis, and staging. To date all FISH detection and dot counting devices are limited by the quality of the images. In addition, many biological problems cannot be characterized by the examination of a single parameter; therefore, it is necessary to be able to detect two or more fluorescent signals in the same tissue or cell. Conventional fluorescence microscopy, confocal microscopy, and deconvolution techniques have been extremely useful for viewing and analyzing labeled DNA, RNA and proteins. Current research and commercially available products focus automatically only on each field of view (FOV). All such focusing techniques are based on optimizing some arbitrary metric (such as contrast or intensity). Hence, such focusing techniques do not lend themselves to producing images with a large depth of field.
Several methods and apparatus are known for adjusting images. For example, U.S. Pat. No. 5,621,495 enhances human feeling and sensitivity to depth of focus. This is accomplished by using conventional optical variation of F-number to achieve the perceived enhancement. U.S. Pat. No. 5,617,257 discloses a technique of using a plate lodged in a housing that is placed in proximity to each objective lens of a binocular arrangement to change the focal range. U.S. Pat. No. 5,483,055 discloses a method and apparatus for performing automatic focus on a confocal microscope. A coarse z-stage movement is used with a threshholded photo-detector to determine focus. This very slow technique, which works only with a conventional confocal microscope, cannot produce an enhanced depth of field in near-real time.
It is an object of the present invention to provide an improved means for producing microscope images having an enhanced depth of field.